288 ALLAN HANCOCK PACIFIC EXPEDITIONS VOL. 15 



pointed seta in irregular arrangement. In partial three-quarter view 

 some of these uncini appear cuspidate on the inner convex edge, as 

 originally shown by Ehlers (pi. 21). 



Furcate setae (fig. 4) are present in posterior thoracic and abdominal 

 notopodia; they have tines of unequal length and a smooth shaft. Ab- 

 dominal neuropodia (fig. 1) have heavy yellow acicula (fig. 2) which 

 project from the distal end of the neuropodium for a short distance; a 

 second developing aciculum may be more deeply embedded. 



In a collection of many individuals from San Quintin Bay, Lower 

 California, the length of the body is more than 60 mm (the posterior 

 ends are fragmented) ; number of segments is more than 300. The thorax 

 is 1.04 mm wide at most and deeply depressed through most of length, 

 so that its width/depth ratio is about 3/1. The prostomium is long and 

 distally pointed and about 1.4 times as long as wide; it has no eyes. 

 The everted proboscis is a large, spacious smooth epithelial pouch that 

 extends across the ventrum of anteriormost segments; there are no ter- 

 minal lobes. The peristomium or first segment is a smooth ring about 

 two-thirds as long as the prostomium. 



Branchiae are first present from the sixth setigerous segment and 

 stand erect with each pair close together in the thorax and thus far 

 removed from the parapodial bases ; they form trim rows on the greatly 

 depressed thorax and are uniform in size and appearance. In the ab- 

 domen they increase in size and are more conspicuously ciliated at their 

 lateral margins. Branchiae are simple lobes throughout. 



The thorax consists of 21 setigerous segments and the change to the 

 abdomen is abrupt thereafter. Thoracic notopodial postsetal lobes are 

 slender, erect and long triangular, but are largely concealed by the 

 much longer notopodial setal fascicle. Thoracic neuropodia have con- 

 spicuous palisaded rows of uncini arranged in about four vertical rows ; 

 they emerge from a low ridge that lacks papillae. The anteriormost 

 uncini number about 10 in a row, are thick and rust-colored due to an 

 extraneous deposit; they are distally bluntly rounded. The two middle 

 rows of uncini more nearly resemble those in the posteriormost row 

 except that they lack a hyaline hood ; in their distal end they are slight- 

 ly curved, have a shallow cuspidate depression immediately beyond the 

 weakly developed transverse rows of ridges (which are hardly visible on 

 most uncini). The posteriormost row of uncini are distally hooded and 

 have transverse rows of delicate ridges at their outer curved side. There 

 are no pointed setae except for an occasional one, resembling the noto- 

 podial setae, accompanying the posteriormost row of uncini. 





